Describes modified peptides at the C-terminus peptide having the formula - Pro - NH-R, wherein R is selected from hydrogen, hydroxy, C1-6 alkyl, hydroxy C1-6 alkyl, and C6-9 arakyle or R is NHR1, wherein R1 is hydrogen C1-6 alkyl, C6-9 aralkyl or CO-R2 group, wherein R2 is selected from NH2, C1-6 alkyl and C6-9 aralkyl, eg calcitonin. Said peptides are prepared by reacting a constituent substrate of the formula Peptide - Pro - X, wherein X is an amino acid having a side chain containing at least two carbon atoms and, in addition, at least one hetero atom selected from N , O and S, with a nucleophile component NH2-R, wherein R has the above meaning in the presence of a serine or L-specific enzyme thiolcarboxypeptidase from yeast or of animal, vegetable or microbial origin , preferably a carboxpeptidase from yeast in a solution or an aqueous dispersion having a pH of between 7.5 and 10, and optionally containing up to 25% of an organic solvent. X is preferably selected from Met, Thr, Tyr, Met (O), His, Gln, Asn, Arg, Lys and Trp. Human calcitonin (1-32) Met-OH is a useful intermediate. The method allows selective C-terminal amidation of peptides in satisfactory yields.
展开▼
